Kansas: In addition to the federal form, students must complete a state "census adjustment" that counts them at their permanent address to determine congressional and state legislative districts. Why? So college towns like Lawrence don't have an edge over rural areas.

Connecticut: A legislative committee asked the Census Bureau in 2000 to correct the location of a University of Hartford dorm after learning that about 2,500 students were counted in the wrong town, which in turn affected the boundary of state House districts.

Massachusetts: The state's estimated 330,000 college students could help determine whether it retains 10 congressional districts; Secretary of State William Galvin has asked the Census to finish its counts before students, many from out of state, leave for the summer. The state could fall short by 70,000 to 150,000 people, so students are "critical," he says.

VIDEO: How the government turns 360 million Census pages into the USA's digital portrait.CLICK HERE

By Mary Beth Marklein, USA TODAY

Until he took a statistics class on it this spring, Christian Reyes barely knew what the U.S. Census was, much less that he has a legal obligation to return a completed form in Pittsburgh, where he is a freshman at Carnegie Mellon University. Now that he has become a bit of an expert on the topic, he suspects most students are similarly unaware.

"Even the people who are supposed to know don't know," says Reyes, 18, who is helping encourage participation in the 2010 count as a class project. He was surprised to find that some student leaders and resident advisers had facts wrong.

Some uncertainty is understandable; most undergrads weren't even teens last time around. But for a variety of reasons, college students present a challenge to the Census Bureau.

For one thing, the timing is terrible. Many students take off for spring break in March, just as the Census campaign gears up. By the time enumerators follow up with non-responders in May, some students may be gone for the summer.

For another, the purpose is to count people based on where they live April 1, and for most traditional undergraduates, that will be a campus address. But some students, and parents, assume they are supposed to be counted in their hometowns. And some international students may mistakenly think they aren't supposed to complete the form at all.

Effect on the community

Privacy laws add another wrinkle. Administrators can't directly hand certain data, including race and gender, to Census takers, though many colleges help coordinate the process in dorms, fraternities and other campus housing.

There are exceptions. The College of Wooster in Ohio, where all but about 20 of 1,700 students live on campus, has arranged to release students' names, birth dates, dates of attendance and campus addresses to the Census. "We don't have to have every question answered in that situation," says the Census' David DeShon.

Practical matters aside, the Census can be a tough sell for other reasons. It "is not necessarily widely recognized as something connected to any of the issues college students feel passionate about," says Wake Forest University sociology professor Ana Wahl, who discusses the Census in classes on race and ethnicity.

Yet for the communities in which they live, the student count can make a big difference.

In Fort Collins, Colo., Colorado State University's 25,000 students represent 18% of the city's 140,000 residents. That translates to more than $200 million in potential federal funding in the next decade; the state's demography office estimates that each person counted brings in $880 a year.

"You start to do the math — what happens if you miss one or 10 or 1,000 students?" asks Ken Waido, the city's chief planner. "It adds up pretty quick."

'Great fear' it isn't confidential

A Fort Collins Census committee has stepped up outreach to students based on a review of past data that leads city officials to believe that, as a group, the 15,000 or so students who live off-campus have the highest probability of being undercounted.

The city faces an added challenge: A 2007 ordinance strengthened a law barring more than three unrelated people from living in a single dwelling. A 2009 study estimated that about 600 households were in violation.

By law, Census officials can't share answers with anyone, including federal, state and local agencies. But students have expressed skepticism. "There's a great fear out there that it's not going to be confidential," says Courtney Sullivan, director of community affairs for the student government.

On a website aimed at students, Census stresses confidentiality. Other key messages: Forms are easy to fill out, and the count affects services such as public transportation and health care as well as college tuition grant and loan programs.

Some regional Census offices also are engaging students through Facebook, podcasts and videos. And that points to one more challenge: Snail mail is hardly the communications mode of choice for students, but it's how forms arrive at most households and how they must be returned.

That may change. But for now, the most effective ways to reach students appear to be both modern and, in some cases, older than the Pony Express. "They're so mobile and electronic ... but they still use fliers, placards and bulletin boards," says University of Texas-Austin professor Keri Stephens, who has a Census Bureau grant to research students' use of communications technology.

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